Locating devices for detecting objects enclosed in a medium are commonly used in trade occupations and in finishing the interior of buildings, for example to locate electrical wiring or water pipes. In addition to carrying out the actual measurement function, the operation of the device is extremely important to the quality of the measurement result. A measuring device of high-quality technology can achieve only a poor measuring performance under practical conditions in the field if it is operated incorrectly by the user, for example if he/she makes incorrect assumptions when operating the device. For example, if the operator makes incorrect assumptions as to the sensor's precise position, it is impossible to accurately mark the location for this reason alone.
A hand-held metal detector which enables the user to qualitatively determine both the position and the depth of a metal object enclosed in a medium is described in German Patent No. DE 42 00 518 A1. In the case of this measuring device, a sensor provided with two coil pairs is used to detect hidden metal, for example in a wall, and determine the depth at which it is embedded. The sensor's two coil pairs are each connected to an oscillator and oscillate continuously at different frequencies. The signals influenced by the metal are measured and weighted for evaluation. An intensity display in the form of a bar graph characterizes the position of the enclosed metal. To mark the detected location of the enclosed metal, the locating device described in German Patent No. DE 42 00 518 A1 has a hole in the active center of the sensor through which, for example, the drill bit of a drilling machine or a marking medium is insertable. In an embodiment of the locating device described in German Patent No. DE 42 00 518 A1, for example, a stamp containing a colorant is movably positioned in this hole for the purpose of marking the detected position, for example on a wall.
A locating device for detecting objects enclosed in a medium, which transmits a directed light signal onto the surface to be examined for the purpose of displaying the position of the enclosed object behind the surface, is described in U.S. Pat. No. 6,259,241 Bl. The device described in U.S. Pat. No. 6,259,241 Bl has one or a plurality of light-emitting diodes which are inserted into the housing and, when activated, can transmit a light signal which is directed onto the object to be examined via corresponding openings in the housing wall. If a sensor of the measuring device detects a corresponding measuring signal, depending on the embodiment of the locating device, either an individual or a plurality of line-shaped light signals are projected onto the object to be examined to thereby reveal to the user the presence and approximate position of the enclosed object.